US 20060279024 A1
The present invention provides a method to reduce adhesion between a conformable region on a substrate and a pattern of a mold, which selectively comes into contact with the conformable region. The method features forming a conformable material on the substrate and contacting the conformable material with the surface. A conditioned layer is formed from the conformable material. The conditioned layer has first and second sub-portions, with the first sub-portion being solidified and the second sub-portion having a first affinity for the surface and a second affinity for the first sub-portion. The first affinity is greater than the second affinity. In this fashion, upon separation of the mold from the conditioned layer, a subset of the second sub-portion maintains contact with the mold, thereby reducing the probability that a pattern formed in the conditioned layer becomes compromised.
11. A method for providing desirable wetting and release characteristics between a mold, having a surface, and a polymerizable composition, said method comprising:
coating said surface with a volume of surfactant containing solution, with said surfactant including a hydrophobic component consisting essentially of a plurality of atoms, with a distribution of said fluorine atoms throughout said volume providing a desired contact angle with respect to said polymerizable composition.
12. The method as recited in
13. The method as recited in
14. The method as recited in
15. The method as recited in
16. A method for providing desirable wetting and release characteristics between a mold, having a surface, and a polymerizable composition, said method comprising:
disposing a layer of a surfactant-containing solution on said surface;
contacting said polymerizable composition with said layer, defining an interface, with said layer and said polymerizable composition each including a surfactant component, with an aggregate quantity of said surfactant component at said interface being sufficient to generate a lamella layer.
17. The method as recited in
The present application is a continuation of U.S. application Ser. No. 10/463,396 (published as U.S. Pat. No. 2004-0256764-A1), filed Jun. 17, 2003, entitled “Method to Reduce Adhesion Between a Conformable Region and a Pattern of a Mold”, listing Byung-Jin Choi, Frank Y. Xu, Nicholas A. Stacey, Van N. Truskett, and Michael P. C. Watts as inventors. This aforementioned patent application is incorporated herein by reference.
The field of invention relates generally to micro-fabrication of structures. More particularly, the present invention is directed to patterning substrates in furtherance of the formation of structures.
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 a reduction in 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 shown in U.S. Pat. No. 6,334,960 to Willson et al. Willson et al. disclose a method of forming a relief image in a structure. The method includes providing a substrate having a transfer layer. The transfer layer is covered with a polymerizable fluid composition. 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 polymerize the same, forming a solidified polymeric material on the 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 transfer layer and the solidified polymeric material are 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.
An important characteristic with accurately forming the pattern in the polymeric material is to reduce, if not prevent, adhesion of the polymeric material, and/or, transfer layer, to the mold. These are referred to as release characteristics. In this manner, the pattern recorded in the polymeric material and/or transfer layer is not distorted during separation of the mold therefrom. To improve the release characteristics, Willson et al. form a release layer on the surface of the mold. The release layer is typically hydrophobic and/or has low surface energy. The release layer adheres to the mold and to either the transfer layer or the polymeric material. Providing the transfer layer with improved release characteristics minimizes distortions in the pattern recorded into the polymeric material and/or the transfer layer that are attributable to mold separation. This type of release layer is referred to, for purposes of the present discussion, as an a priori release layer, i.e., a release layer that is solidified to the mold.
Another prior art attempt to improve release characteristics is described by Bender et al. in Multiple Imprinting in UV-based Nanoimprint Lithography: Related Material Issues, Microeletronic Engineering 61-62 (2002), pp. 407-413. Specifically, Bender et al. employ a mold having an a priori release layer in conjunction with a fluorine-treated UV curable material. To that end, a UV curable layer is applied to a substrate by spin-coating a 200 CPS UV curable fluid to form a UV curable layer. The UV curable layer is enriched with fluorine groups to improve the release characteristics.
A priori release layers, however, typically have a limited operational life. As a result, a single mold may be coated multiple times with an a priori release layer. This can result in several hours of down-time for a given mold, reducing throughput. Additionally, the molecular structure of the a priori release layer may limit the minimization of the minimum feature dimension that is printed.
There is a need, therefore, to improve the release characteristics of a mold employed in imprint lithography processes.
The present invention provides a method to reduce adhesion between a substrate and a pattern of a mold. The method features forming a conformable material on the substrate and contacting the conformable material with the surface. A conditioned layer is formed from the conformable material. The conditioned layer has first and second sub-portions, with the first sub-portion being solidified and the second sub-portion having a first affinity for the surface and a second affinity for the first sub-portion. The first is greater than the second affinity. In this fashion, upon separation of the mold from the conditioned layer, a subset of the second sub-portion maintains contact with the mold, thereby reducing the probability that a pattern formed in the conditioned layer becomes compromised. These and other embodiments are described herein.
Referring to both
Referring to both
To facilitate filling of recessions 28 a, material 36 a is provided with the requisite properties to completely fill recessions 28 a while covering surface 32 with a contiguous formation of material 36 a. In the present embodiment, sub-portions 34 b of imprinting layer 34 in superimposition with protrusions 28 b remain after the desired, usually minimum distance “d”, has been reached, leaving sub-portions 34 a with a thickness t1, and sub-portions 34 b with a thickness, t2. Thicknesses “t1” and “t2” may be any thickness desired, dependent upon the application. Typically, t1 is selected so as to be no greater than twice the width u of sub-portions 34 a, i.e., t1 ≦2 u, shown more clearly in
To that end, imprinting layer 134 may 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 layer 134, using known techniques. Any etch process may be employed, dependent upon the etch rate desired and the underlying constituents that form substrate 31 and imprinting layer 134. Exemplary etch processes may include plasma etching, reactive ion etching, chemical wet etching and the like.
Referring to both
The constituent components that form material 36 a to provide the aforementioned characteristics may differ. This results from substrate 31 being formed from a number of different materials. As a result, the chemical composition of surface 32 varies dependent upon the material from which substrate 31 is formed. For example, substrate 31 may be formed from silicon, plastics, gallium arsenide, mercury telluride, and composites thereof. Additionally, substrate 31 may include one or more layers in sub-portion 34 b, e.g., dielectric layer, metal layer, semiconductor layer, planarization layer and the like.
To improve the release properties of mold 28 and imprinting layer 34 and to ensure that imprinting layer 34 does not adhere to mold 28, the composition from which material 36 a is formed may include an additive that reduces the surface tension of COMPOSITION 1. To that end, material 36 a may include, as an additive, a surfactant. For purposes of this invention a surfactant is defined as any molecule, one tail of which is hydrophobic. Surfactants may be either fluorine containing, e.g., include a fluorine chain, or may not include any fluorine in the surfactant molecule structure. An exemplary surfactant is a non-ionic surfactant available under the trade name ZONYL® FSO-100 from DUPONT™ that has a general structure of R1R2 where R1 =F(CF2CF2)Y, with y being in a range of 1 to 7, inclusive and R2=CH2CH2O(CH2CH2O)xH, where X is in a range of 0 to 15, inclusive. This provides material 36 a with the following composition:
An advantage provided by COMPOSITION 2 is that it abrogates the need for an a priori release layer, i.e., a separate hydrophobic and/or low surface energy release layer disposed on mold 28. Specifically, COMPOSITION 2 provides desirable release properties to mold 28 and imprinting layer 34 so that material 36 c, shown in
Specifically, interface 136 a defines a first interfacial energy step associated therewith, and second interface 137 a defines a second interfacial energy step, with the first interfacial energy step being greater than the second interfacial energy step. The first interfacial energy step is defined by the difference in surface energy of mold 28 and surface tension of material 36 c in region 136. The second interfacial surface energy is defined by the adhesion of material 36 c associated with region 136 for material 36 c associated with region 137. In the present example, COMPOSITION 2 provides region 136 with a surface tension in a range of 20-35 milli-Newtons/meter, with one milli-Joule/cm2 =1 milli-Newton/meter. As a result, the interfacial surface energy step at interface 136 a is sufficiently large to overcome the interfacial energy step at interface 137.
Another manner by which to improve the release properties of mold 28 includes conditioning the pattern of mold 28 by exposing the same to a conditioning mixture including an additive that will remain on mold 28 to reduce the surface energy of the mold surface. An exemplary additive is a surfactant.
In a specific example, mold 28 was exposed to a mixture that included approximately 0.1% or more of ZONYL® FSO-100 with the remainder comprising isopropyl alcohol (IPA). Exposure of the pattern may be achieved by virtually any manner known in the art, including dipping the pattern into a volume of the conditioning mixture, wiping the pattern with a cloth saturated with the conditioning mixture and spraying a stream of the conditioning mixture onto the surface. The IPA in the conditioning mixture is then allowed to evaporate before using the mold 28. In this manner, the IPA facilitates removing, from the pattern, undesired contaminants while leaving the additive, thereby conditioning the surface of the pattern. The conditioning mixture may be employed with COMPOSITION 2 to augment improvement of the release properties provided by COMPOSITION 2. The additive in the conditioning mixture may be the same or differ from the additive in COMPOSITION 2. Alternatively, the conditioning mixture may be employed with COMPOSITION 1, or any other polymerizable material suitable for imprint lithography, as well as other imprint processes such as the hot embossing and laser assisted imprint processes.
Another technique for conditioning the pattern of mold 28 employs pattern priming. Pattern priming is achieved by selectively contacting the conformable region with the pattern a sufficient number of times to accurately reproduce, in the conformable region, a pattern complementary to the initial pattern. Specifically, it was found that by repeatably contacting imprint material 36 a, shown in
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. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.