Abstract
A method of reducing the dimension of an imprint structure on a substrate, the method comprising the steps of: (a) providing a substrate having at least one imprint structure thereon, said structure being formed of an inorganic-organic compound comprising an inorganic moiety and a polymer moiety, said polymer moiety having a lower vaporization temperature than the melting point of said inorganic moiety; and (b) selectively removing at least part of the polymer moiety while enabling at least part of the inorganic moiety to form a substantially continuous inorganic phase in said imprint structure, wherein the removal of the at least part of the polymer moiety from the imprint structure reduces the dimension of the imprint structure.
Claims
1. A method of reducing a dimension of an imprint structure on a substrate, the method comprising the steps of: (a) coating a monomer-composite composition comprising an admixture of a polymerizable monomeric composition and an inorganic moiety on said substrate; (b) contacting a mold having an imprint-forming surface with said monomer-composite composition, wherein said substrate and said mold are not the same; (c) polymerizing said monomer-composite composition while in contact with said mold to form an imprint structure formed of an inorganic-organic compound comprising said inorganic moiety and a polymer moiety, said polymer moiety having a lower vaporization temperature than the melting point of said inorganic moiety on said substrate; (d) removing said mold from said imprint structure; and (e) selectively removing at least part of the polymer moiety while enabling at least part of the inorganic moiety to form a substantially continuous inorganic phase in said imprint structure, wherein the removal of the at least part of the polymer moiety from the imprint structure reduces the dimension of the imprint structure, wherein said inorganic moiety does not include silicon.
2. The method as claimed in claim 1, wherein the selectively removing step (e) comprises the step of heating said imprint structure.
3. The method as claimed in claim 1 or 2, wherein the inorganic moiety is substantially homogenously dispersed throughout said polymer moiety.
4. The method as claimed in claim 1, comprising the step of providing said polymer moiety being comprised of at least one of an allyl, a vinyl or an acrylate polymer.
5. The method as claimed in claim 1, wherein the inorganic moiety comprises at least one of a metal or metalloid.
6. The method as claimed in claim 5, wherein the metal or metalloid is selected from the group consisting of Titanium, Zirconium, Niobium, Tantalum, Iron, Copper, Silver, and Zinc.
7. The method as claimed in claim 1, wherein the imprint structure is: (i) a generally elongate imprint having a length dimension parallel to a longitudinal axis that is generally parallel to said substrate, said length dimension being defined between a proximal end and a distal end; or (ii) a projection having a longitudinal axis that is generally normal to said substrate and wherein the projection extends from a proximal end from said substrate to a distal end.
8. The method as claimed in claim 7, wherein the length dimension is at least two folds greater than the width dimension of the imprint.
9. The method as claimed in claim 1, wherein, after said selectively removing step, the imprint structure has at least one of the following properties: (i) the imprint structure has substantially the same aspect ratio as the imprint before the selectively removing step; and/or (ii) the imprint structure has a dimension that is reduced by at least 30% of the dimension of the imprint structure before said selectively removing step.
10. The method as claimed in claim 1, wherein an array of imprints is disposed on said substrate.
11. The method as claimed in claim 10, wherein the array is an ordered array of a series of rows and columns of imprints being disposed on said substrate at an approximately equal distance from each other.
12. The method as claimed in claim 7, wherein each imprint has a centre point defined along a central longitudinal axis and between said proximal and distal ends, and wherein the center point between adjacent imprints does not substantially change during said selectively removing step.
13. The method as claimed in claim 1, wherein said polymerizing step is undertaken at a temperature of from 60 degrees Celsius to 150 degrees Celsius.
14. The method as claimed in claim 1, wherein the polymerizing step is carried out in the presence of ultra-violet radiation.
15. The method as claimed in claim 1, wherein the selectively removing step is carried out at a temperature of from 300 degrees Celsius to 900 degrees Celsius.
16. The method as claimed in claim 1, wherein the imprint after said selectively removing step has a dimension in the nanoscale size range.
17. The method as claimed in claim 1, comprising the step of providing a minimum amount of inorganic moiety in the inorganic-organic compound such that after said polymer moiety has been selectively removed, the shape of the imprint is substantially the same.
18. The method as claimed in claim 17, wherein the step of providing a minimum amount of inorganic moiety in the inorganic-organic compound comprises reacting an inorganic compound with at least one of an allyl, a vinyl, a methacrylic or an acrylic acid in a molar ratio of about 1:8 to about 1:2.
19. The method as claimed in claim 18, wherein the inorganic compound is at least one of a metal alkoxide and a metalloid alkoxide.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1) The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.
(2) FIG. 1 is a schematic diagram illustrating the method in accordance to one embodiment of the disclosed method.
(3) FIG. 2a is a scanning electron microscope (SEM) image at 10,000 magnification of a substrate according to one embodiment of the disclosed method, with linear imprint structures of about 250 nm line width comprising polymerized Titanium methacrylate, before heat-treatment.
(4) FIG. 2b is a scanning electron microscope (SEM) image at 10,000 magnification of the substrate as shown in FIG. 2a, after heat-treatment.
(5) FIG. 3a is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 2a.
(6) FIG. 3b is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 2b.
(7) FIG. 4a is a scanning electron microscope (SEM) image at 10,000 magnification of a substrate according to one embodiment of the disclosed method, with columnar imprint structures of about 200 nm diameter comprising polymerized Titanium methacrylate, before heat-treatment.
(8) FIG. 4b is a scanning electron microscope (SEM) image at 10,000 magnification of the substrate as shown in FIG. 4a, after heat-treatment.
(9) FIG. 5a is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 4a.
(10) FIG. 5b is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 4b.
(11) FIG. 6a is a scanning electron microscope (SEM) image at 30,000 magnification of a substrate according to one embodiment of the disclosed method, with linear imprint structures of about 100 nm line width comprising polymerized Titanium methacrylate, before heat-treatment.
(12) FIG. 6b is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 6a, after heat-treatment.
(13) FIG. 7a(i) is a scanning electron microscope (SEM) image at 10,000 magnification of a substrate according to one embodiment of the disclosed method, with linear imprint structures of about 100 nm line width comprising polymerized Zirconium methacrylate.
(14) FIG. 7a(ii) is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 7a(i).
(15) FIG. 7b(i) is a scanning electron microscope (SEM) image at 10,000 magnification of the substrate as shown in FIG. 7a(i), after heat-treatment.
(16) FIG. 7b(ii) is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 7b(i).
(17) FIG. 8a(i) is a scanning electron microscope (SEM) image at 10,000 magnification of a substrate according to one embodiment of the disclosed method, with linear imprint structures of about 100 nm line width comprising polymerized Niobium methacrylate.
(18) FIG. 8a(ii) is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 8a(i).
(19) FIG. 8b(i) is a scanning electron microscope (SEM) image at 10,000 magnification of the substrate as shown in FIG. 8a(i), after heat-treatment.
(20) FIG. 8b(ii) is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 8b(i).
(21) FIG. 9a(i) is a scanning electron microscope (SEM) image at 10,000 magnification of a substrate according to one embodiment of the disclosed method, with linear imprint structures of about 100 nm line width comprising polymerized Tantalum methacrylate.
(22) FIG. 9a(ii) is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 9a(i).
(23) FIG. 9b(i) is a scanning electron microscope (SEM) image at 10,000 magnification of the substrate as shown in FIG. 9a(i), after heat-treatment.
(24) FIG. 9b(ii) is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 9b(i).
(25) FIG. 10a(i) is a scanning electron microscope (SEM) image at 10,000 magnification of a substrate according to one embodiment of the disclosed method, with linear imprint structures of about 100 nm line width comprising polymerized Iron methacrylate.
(26) FIG. 10a(ii) is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 10a(i).
(27) FIG. 10b(i) is a scanning electron microscope (SEM) image at 10,000 magnification of the substrate as shown in FIG. 10a(i), after heat-treatment.
(28) FIG. 10b(ii) is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 10b(i).
(29) FIG. 11a(i) is a scanning electron microscope (SEM) image at 10,000 magnification of a substrate according to one embodiment of the disclosed method, with linear imprint structures of about 100 nm line width comprising polymerized Silicon methacrylate.
(30) FIG. 11a(ii) is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 11a(i).
(31) FIG. 11b(i) is a scanning electron microscope (SEM) image at 10,000 magnification of the substrate as shown in FIG. 11a(i), after heat-treatment.
(32) FIG. 11b(ii) is a scanning electron microscope (SEM) image at 30,000 magnification of the substrate as shown in FIG. 11b(i).
EXAMPLE
(33) Non-limiting examples of the invention will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.
(34) Without being bound by theory, it is believed that the current invention proceeds via the following reaction pathway, wherein Titanium methacrylate monomer is polymerized to form imprint structures comprising a polymethacrylate polymer moiety in which Titanium is evenly distributed. Said imprint structures are subsequently treated with heat to substantially remove the polymer moiety, leaving imprint structures of reduced dimensions in which Titanium and its oxides form a substantially continuous phase.
(35) ##STR00001##
A) Metal Methacylate Synthesis
(36) TiMA is prepared by reacting Titanium n-butoxide (Ti(OBu.sup.n).sub.4) and methacrylic acid (MAA) in a ratio of molar ratio of 1:4. Ti(OBu.sup.n).sub.4, MAA and ethylene glycol dimethacrylate (EDMA) are procured from a supplier such as Aldrich. Ti(OBu.sup.n).sub.4 and MAA are used without further purification, while EDMA is first passed through an alumina column in order to remove any stabilizers. Next, Ti(OBu.sup.n).sub.4, MAA and EDMA are mixed together (molar ratio of Ti(OBu.sup.n).sub.4:MAA:EDMA=1:4:2). A red solution results. After mixing, azobis(isobutyronitrile) (AIBN) is added in the amount of 2 wt % of MAA and EDMA. This mixture is termed an imprintable TiMA-EDMA mixture.
(37) B) Metal Methacrylate Imprinting
(38) Prior to imprinting, silicon substrates and molds are cleaned, mold treatment is performed and films formed using spin coating. The full procedure is as follows.
(39) First, silicon substrates are cleaned with piranha solution at 140 C. for 2 hours, followed by rinsing with deionized water and blow drying by nitrogen air gun. The substrates are placed in a drying oven to remove any remaining moisture on the surface. The dimension of substrates used is 1 cm1 cm.
(40) Second, three types of standard silicon molds with different patterns are prepared for use. The first two are grating molds with line widths of 250 nm and 100 nm, generating line and space imprint patterns. The third is a dimple mold that generates a pillar and line pattern with pillars of 200 nm diameter by 100 nm height. The molds are treated in oxygen plasma (100RF, 200 torr) for 10 min. After plasma treatment, the mold is cleaned by piranha solution at 140 C. for 2 hours, followed by rinsing with deionized water and blow drying by nitrogen air gun. They are placed in a drying oven to remove any remaining moisture on the surface. A 20 mM solution of perfluorodecyltrichlorosilane (FDTS) in a vacuum desiccator was used to silanize the molds for 5 hours. The silanization treatment is used to reduce the surface energy of the molds to facilitate the demolding process.
(41) Third, a uniform film of the imprintable TiMA-EDMA mixture is coated onto the substrate by spin-coating of the liquid TiMA-EDMA mixture at 800 rpm for 30 seconds.
(42) Finally, the imprintable TiMA-EDMA film on the substrate is imprinted with the mold. The imprinting system used is a pressure chamber with isotropic pressure, which allows pressing force to be delivered to a large area substrate effectively and uniformly. This process was carried out in an Obducat imprinter (Obducat, Sweden). The imprinting was carried out in two stepsthe mold is initially brought into contact with the imprintable TiMA-EDMA film for 300 secs at a temperature of 30 C. and a pressure of 10 bars. Subsequently, without releasing the pressure, the film and the mold are heated to 110 C. for 180 secs in order to induce polymerization. Thereafter, it is cooled down to 20 C. before the pressure is released and the mold removed.
(43) Following a clean demolding, imprinting yield of >90% was observed. The imprinted substrate is then heat treated at a temperature of 400 C. in a furnace in air. The results were analyzed by a scanning electron microscope (SEM) as shown in FIG. 2 through 6 described in more detail further below.
(44) Upon further examination of the cross section by atomic force microscopy, it was found that both the polymerization step and the heat-treatment step caused shrinkage in feature sizes. The heat-treatment step caused feature shrinkage of between 33% and 74% relative to the imprint structures before heat-treatment, as summarized in the following table.
(45) TABLE-US-00001 TABLE 1 Summary of the approximate feature size reduction at every step of the TiO.sub.2 patterning using imprint lithography Feature size of the imprint after Oxide feature size after the heat- Total feature size free redical polymerization treatment of imprinted structures reduction with Width of Feature size Width of the Feature size respect to mold Mold shape/size imprint (nm) reduction (%) oxide feature (nm) reduction (%) features size (%) Dimples, 200 nm 120 40% 80 33% 60% Lines, 250 nm 230 8% 60 74% 76% Lines, 100 nm 70 30% 20 72% 80%
DETAILED DESCRIPTION OF DRAWINGS
(46) Referring to FIG. 1, there is provided a schematic diagram illustrating the method in accordance to one embodiment of the disclosed method. In step D, a silicon substrate 30 is provided having at least one imprint structure 21a which is part of an array of one or more imprint structures 21.
(47) The array of imprint structures is formed by steps A through C, from a silicon substrate 30 in step A, initially spin coated with a layer 20 of a monomer-composite composition comprising an admixture of a titanium methacrylate, ethylene glycol dimethacrylate (crosslinker), azobis-isobutyronitrile (initiator). In step B, a silicon or a quartz mold 10 with an imprint-forming surface 10a is contacted with layer 20 under pressure of 1000 kPa for 300 seconds, such that the monomer-composite composition takes the shape of the mold 10 in layer 20. In step C, the assembly of 10, 20 and 30 are brought to a temperature of 110 C. for 180 seconds such that layer 20 undergoes polymerization to form said array of imprint structures 21.
(48) At this point, referring to step D, the mold 10 is removed, leaving substrate 30 with one or more imprint structures thereon, said imprint structures 21 comprising a titanium component dispersed in a polymethacrylate polymer moiety. In step E, imprint structures 21 are heat-treated at 400 C. in a furnace in air to selectively remove the organic matter from the polymethacrylate polymer moiety by oxidation and vaporization, while leaving behind titanium oxide in imprint structures of reduced size, 22. Individual imprint structures 22a are now reduced in dimension relative to imprint structures before heat-treatment, 21a.
(49) Referring to FIGS. 2a and 2b, there are provided scanning electron microscope (SEM) images at 10,000 magnification of a substrate comprising polymerized Titanium methacrylate and having linear imprint structures with line widths of about 250 nm in accordance to one embodiment of the disclosed method, before and after heat-treatment respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 250 nm before heat-treatment, to reduced line widths of about 70 nm after heat-treatment. It will also be noted from the images in FIG. 2a and FIG. 2b that the shape of the imprints before and after the heat-treatment step remained substantially the same.
(50) Referring to FIGS. 3a and 3b there are provided scanning electron microscope (SEM) images at 30,000 magnification of the substrate of FIG. 2a and FIG. 2b respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 250 nm before heat-treatment, to reduced line widths of about 70 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. That is, it can be seen from the images in FIG. 3a and FIG. 3b that the shape of the imprints before and after the heat-treatment step remained substantially the same. Also, the center to center distances between adjacent structures do not substantially change.
(51) Referring to FIG. 4a and FIG. 4b there are provided scanning electron microscope (SEM) images at 10,000 magnification of a substrate comprising polymerized Titanium methacrylate and having columnar imprint structures with columnar diameters of 200 nm in accordance with one embodiment of the disclosed method, before and after heat-treatment respectively. Significant shrinkage in feature dimensions can be seen, from columnar diameters of about 200 nm before heat-treatment, to reduced columnar diameters of about 70 nm after heat-treatment.
(52) Referring to FIG. 5a and FIG. 5b, there are provided scanning electron microscope (SEM) images at 30,000 magnification of the substrate of FIG. 4a and FIG. 4b respectively. Significant shrinkage in feature dimensions can be seen, from columnar diameters of about 200 nm before heat-treatment, to reduced columnar diameters of about 70 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. That is, it can be seen from the images in FIG. 5a and FIG. 5b that the shape of the imprints before and after the heat-treatment step remained substantially the same. Also, the center to center distances between adjacent structures do not substantially change.
(53) Referring to FIG. 6a and FIG. 6b there are provided scanning electron microscope (SEM) images at 30,000 magnification of a substrate comprising polymerized Titanium methacrylate and having linear imprint structures with line widths of about 100 nm in accordance to one embodiment of the disclosed method, before and after heat-treatment respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 100 nm before heat-treatment, to reduced line widths of about 30 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. That is, it can be seen from the images in FIG. 6a and FIG. 6b that the shape of the imprints before and after the heat-treatment step remained substantially the same. Also, the center to center distances between adjacent structures do not substantially change.
(54) Referring to FIG. 7a(i) and FIG. 7b(i), there are provided scanning electron microscope (SEM) images at 10,000 magnification of a substrate comprising polymerized Zirconium methacrylate and having linear imprint structures with line widths of about 250 nm in accordance to one embodiment of the disclosed method, before and after heat-treatment at 400 degrees Celsius respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 250 nm before heat-treatment, to reduced line widths of about 70 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. The rectangular sections of the substrate as indicated in FIG. 7a(i) and FIG. 7b(i) are further magnified in FIG. 7a(ii) and FIG. 7b(ii), respectively.
(55) Referring to FIG. 7a(ii) and FIG. 7b(ii), there are provided scanning electron microscope (SEM) images at 30,000 magnification of the substrate of FIG. 7a(i) and FIG. 7b(i) respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 250 nm before heat-treatment, to reduced line widths of about 70 nm after heat-treatment. Also, pitch widths expand from about 250 nm before heat-treatment to about 430 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. That is, it can be seen from the images in FIG. 7a(ii) and FIG. 7b(ii) that the shape of the imprints before and after the heat-treatment step remained substantially the same. Also, the center to center distances between adjacent structures do not substantially change as well. After said heat-treatment, imprint structures show shrinkage of about 72%, while pitch widths between adjacent imprint structures show an increase of 72%.
(56) Referring to FIG. 8a(i) and FIG. 8b(i), there are provided scanning electron microscope (SEM) images at 10,000 magnification of a substrate comprising polymerized Niobium methacrylate and having linear imprint structures with line widths of about 250 nm in accordance to one embodiment of the disclosed method, before and after heat-treatment at 400 degrees Celsius respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 250 nm before heat-treatment, to reduced line widths of about 140 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. The rectangular sections of the substrate as indicated in FIG. 8a(i) and FIG. 8b(i) are further magnified in FIG. 8a(ii) and FIG. 8b(ii), respectively.
(57) Referring to FIG. 8a(ii) and FIG. 8b(ii), there are provided scanning electron microscope (SEM) images at 30,000 magnification of the substrate of FIG. 8a(i) and FIG. 8b(i) respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 250 nm before heat-treatment, to reduced line widths of about 140 nm after heat-treatment. Also, pitch widths expand from about 250 nm before heat-treatment to about 360 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. That is, it can be seen from the images in FIG. 8a(ii) and FIG. 8b(ii) that the shape of the imprints before and after the heat-treatment step remained substantially the same. Also, the center to center distances between adjacent structures do not substantially change as well. After said heat-treatment, imprint structures show shrinkage of about 44%, while pitch widths between adjacent imprint structures show an increase of 44%.
(58) Referring to FIG. 9a(i) and FIG. 9b(i), there are provided scanning electron microscope (SEM) images at 10,000 magnification of a substrate comprising polymerized Tantalum methacrylate and having linear imprint structures with line widths of about 250 nm in accordance to one embodiment of the disclosed method, before and after heat-treatment at 400 degrees Celsius respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 250 nm before heat-treatment, to reduced line widths of about 80 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. The rectangular sections of the substrate as indicated in FIG. 9a(i) and FIG. 9b(i) are further magnified in FIG. 9a(ii) and FIG. 9b(ii), respectively.
(59) Referring to FIG. 9a(ii) and FIG. 9b(ii), there are provided scanning electron microscope (SEM) images at 30,000 magnification of the substrate of FIG. 9a(i) and FIG. 9b(i) respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 250 nm before heat-treatment, to reduced line widths of about 80 nm after heat-treatment. Also, pitch widths expand from about 250 nm before heat-treatment to about 420 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. That is, it can be seen from the images in FIG. 9a(ii) and FIG. 9b(ii) that the shape of the imprints before and after the heat-treatment step remained substantially the same. Also, the center to center distances between adjacent structures do not substantially change as well. After said heat-treatment, imprint structures show shrinkage of about 68%, while pitch widths between adjacent imprint structures show an increase of 68%.
(60) Referring to FIG. 10a(i) and FIG. 10b(i), there are provided scanning electron microscope (SEM) images at 10,000 magnification of a substrate comprising polymerized Iron methacrylate and having linear imprint structures with line widths of about 250 nm in accordance to one embodiment of the disclosed method, before and after heat-treatment at 400 degrees Celsius respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 250 nm before heat-treatment, to reduced line widths of about 70 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. The rectangular sections of the substrate as indicated in FIG. 10a(i) and FIG. 10b(i) are further magnified in FIG. 10a(ii) and FIG. 10b(ii), respectively.
(61) Referring to FIG. 10a(ii) and FIG. 10b(ii), there are provided scanning electron microscope (SEM) images at 30,000 magnification of the substrate of FIG. 10a(i) and FIG. 10b(i) respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 250 nm before heat-treatment, to reduced line widths of about 80 nm after heat-treatment. Also, pitch widths expand from about 250 nm before heat-treatment to about 430 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. That is, it can be seen from the images in FIG. 10a(ii) and FIG. 10b(ii) that the shape of the imprints before and after the heat-treatment step remained substantially the same. Also, the center to center distances between adjacent structures do not substantially change as well. After said heat-treatment, imprint structures show shrinkage of about 72%, while pitch widths between adjacent imprint structures show an increase of 72%.
(62) Referring to FIG. 11a(i) and FIG. 11b(i), there are provided scanning electron microscope (SEM) images at 10,000 magnification of a substrate comprising polymerized Silicon methacrylate and having linear imprint structures with line widths of about 250 nm in accordance to one embodiment of the disclosed method, before and after heat-treatment at 400 degrees Celsius respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 250 nm before heat-treatment, to reduced line widths of about 80 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. The rectangular sections of the substrate as indicated in FIG. 11a(i) and FIG. 11b(i) are further magnified in FIG. 11a (ii) and FIG. 11b(ii), respectively.
(63) Referring to FIG. 11a(ii) and FIG. 11b(ii), there are provided scanning electron microscope (SEM) images at 30,000 magnification of the substrate of FIG. 11a(i) and FIG. 11b(i) respectively. Significant shrinkage in feature dimensions can be seen, from line widths of about 250 nm before heat-treatment, to reduced line widths of about 80 nm after heat-treatment. Also, pitch widths expand from about 250 nm before heat-treatment to about 420 nm after heat-treatment. Furthermore, it can also be seen that the center point between adjacent imprint structures does not change substantially after said heat-treatment. That is, it can be seen from the images in FIG. 11a(ii) and FIG. 11b(ii) that the shape of the imprints before and after the heat-treatment step remained substantially the same. Also, the center to center distances between adjacent structures do not substantially change as well. After said heat-treatment, imprint structures show shrinkage of about 68%, while pitch widths between adjacent imprint structures show an increase of 68%.
APPLICATIONS
(64) The disclosed method of reducing the dimension of an imprint structure on a substrate is a simple yet effective way of obtaining imprint structures in the nanoscale range, particularly 100 nm or less. Advantageously, the disclosed method is capable of directly forming imprint structures of metal/metalloid and metal/metalloid oxides on a silicon substrate without the step of etching. More advantageously, the substrate having the imprint structures of metal/metalloid and metal/metalloid oxides formed by the disclosed method may be used in solar cells, sensors, displays, bit pattern media and ferroelectric random access memory (FeRAM). In addition, the ability of the disclosed method to directly pattern semiconductor oxides such as silicon dioxide (SiO2) makes it also useful for fabricating nanopatterned molds. Accordingly, the fabrication of nanofeatured molds may be carried out by the disclosed method without relying on relatively more expensive methods like electron-beam etching and focused-ion beam etching.
(65) As the disclosed method is able to directly pattern the substrate with metals and metal oxides without the need of additional steps such as etching, defects arising from elaborative methods of etching may be avoided. Furthermore, the disclosed method requires relatively less steps to form nano-sized structures than known methods, thus enhancing throughput relative to such known methods.
(66) Advantageously, the disclosed method allows molds with imprint-forming features of micro size to be used to produce final imprint structures of nano size. Advantageously, this translates to overall operational costs savings as the molds with smaller forming features are relatively more expensive than those with larger imprint forming features.
(67) While reasonable efforts have been employed to describe equivalent embodiments of the present invention, it will be apparent to the person skilled in the art after reading the foregoing disclosure, that various other modifications and adaptations of the invention may be made therein without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.
