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A Novel Lithographic Material Constructed by Polymerizable Liquid Crystal Molecule Hui Cao, Hai Deng * Department of Macromolecular Science, State Key Laboratory of Molecular Engineering of Polymers㧘Fudan University Shanghai, China Phone number: 18280304058, E-mail:[email protected] * Corresponding author: [email protected] Biography Hui Cao earned her B.S. degree in polymer science and engineering at the Sichuan University in 2016. She is currently pursuing a master under the guidance of Dr. Hai Deng in Fudan University. Her research mainly focuses on synthesis and directed self-assembly (DSA) of polymerizable liquid crystal and controlling the orientation of liquid crystal in thin films. Abstract This study is aimed at bringing up a novel approach to form higher-resolution patterns which can be used in the lithography field. The idea is operated through taking advantage of the arranging ability of liquid crystal molecules. A polymerizable liquid crystal molecule with specific structure is synthesized at first, then POM and SAXS are done to confirm the specific morphology of the molecule, and application in lithography will be accomplished in the near future. With the continuous stream of integrated circuits with significant size reduction, traditional photolithographic methodologies are thwarted to reduced feature sizes. Meanwhile, other existing methods or materials still have their own shortcomings. Therefore, a new method needs to be conceived to form long-order patterns with small feature sizes. Keywords—polymerizable liquid crystal molecules; lithography; self-assembly; morphology
Introduction The sustained shrinking of device components is an embodiment of human progress that has led to an explosion of micro- and nanotechnologies. In order to support the rapid development of microelectronics industry, manufacturing process has been developed to the size of 10nm node [1]. In an effort to overcome the size limitations facing top-down microelectronics fabrication , several methods including EUV (extreme ultraviolet)ޔDSA (Directed self-assembly) have been proposed in these years. Extreme ultraviolet (EUV) lithography was first put forward in 1980’s by Hawryluk and Seppala [2]. Gwyn suggested that these extensions are relied on incremental decreases in illumination wavelength and increases in optical numerical aperture (NA) for the system [3]. Extreme ultraviolet lithography (EUVL) based on the industrial optical experience uses 10–14 nm extreme ultraviolet light and is expected to support IC fabrication at 10 nm. Though EUVL has several advantages such as good depth of focus, this technique is still
plagued by large capital investments, source power limitations, resist outgassing complications and its considerable cost [4]. Block copolymer (BCP)-based nanopatterning has paved a strong foundation in nanotechnology including nanoporous membranes, patterned magnetic media, and nanolithography. These materials have attracted much attention because of there excellent self-assembly ability. A previous research of Leibler showed that there were three important physical parameters dictating the self-organizing behavior of di-block copolymers: the Flory−Huggins interaction parameter, χ; the overall degree of polymerization, N; and the polymer composition, expressed as the volume fraction of block A (fA) or block B (fB) [5]. With the view of the Leibler’s theory, many researchers are inclined to focus di-block copolymers that have high χ and low N. Unfortunately, an immiscibility-driven approach will not suffice when sub-5 nm periodicities are desired, preventing extendibility to smaller dimensions. In addition, although the assembly of block copolymers can be directed within a photolithographic prepattern, the formation of defect-free periodic structures remains a challenge. [6-8]. Lyotropic liquid crystal (LLC) mesogens are amphiphilic molecules containing a hydrophobic organic tail section and a hydrophilic headgroup [9-10]. Depending on the overall shape and the interfacial curvature energy of the system, monodisperse aqueous domains ranging in structure from lamellae to cylindrical channels with dimensions in the 1–10 nm size range can be formed [11]. As early as 1975Ekwallp has put forward that the smectic phase formed by lyotropic liquid crystals is a lamellar structure with periodically repeated surfactant layers [12].liquid crystalline ordering suggests the possibility of long-ranged pattern formation with very small resolution and few defects, which can’t get from di-block polymers [13].These special materials have the advantage that they can be easily aligned into defect free and sub-5 nm patterns [14]. Exciting work has been performed on the confinement of liquid crystals in structures such as microchannels,[15] nanogrooves,[16] or nanopores,[17] but the directed self-assembly of thin films with sub-5 nm periodicities has not been reported. Therefore, this study synthesized some kinds of polymerizable liquid crystal molecule to form the target lamellar template with photolithography value, which could also provide a new idea for the design and construction of lithography materials. Experiment and discussion In this study, we synthesized a kind of polymerizable LLC
molecule, the synthetic route and molecule structure are shown in Fig.1. The structure has been confirmed by NMR, 1H NMR (400 MHz, d5-methanol): ¥7.27 (s, 2H), 5.82 (dd, 3H),5.03 (dd, 3H), 4.96 (dd, 3H), 4.08 (t, 6H), 3.95 (t, 6H), 1.52 (m, 56 H). Then we mixed the LLC molecule with appropriate amount of water to form ordered structure at the same time explore the impact of water. The effect of different water contents has been studied. When the LLC monomer content is 80%, the target lamellar phase can be obtained, as shown in Fig.2. When the LLC monomer content is lower, a mixed structure occurs, in which we guess it exists lamellar and hexagonal structure simultaneously. With the reduction of water content, lamellar is disappeared while hexagonal is appeared, as shown in Fig.3. Since the monomer has three double bonds, after crosslinking the original ordered structure can be maintained. The crosslinking process needs photoinitiator and a UV light source with a wavelength of 365nm. Then after some specific processing, the polymer free-standing film is able to have the potential value as a mask that can be applied in the lithography field. In the next step, we will try to introduce this LLC molecule into a prepared template made by EBM to explore its further application, which may be not only limited in the lithography field.
Fig. 2 (a) SAXS profile of 80% LLC monomer
Fig. 2 (b) POM image of 80% LLC monomer
Fig. 1 (a) LLC Monomer synthetic route
Fig. 2 When the LLC monomer content is 80%, the lamellar structure is obtained, as shown by the SAXS(a) and POM results(b).
Fig. 1 (b) NMR result of the final product. Fig. 1 LLC Monomer synthetic route (a) and NMR result of the final product (b).
Fig. 3 When the LLC monomer content is 60%, the hexagonal structure is obtained, as shown by the SAXS result.
Conclusions
Through the multi-step synthesis, a liquid crystal molecule with polymerization ability is successfully obtained. After adjusting the concentration of deionized water and crosslinking, the polymer mask with lamellar structure which has value being used in lithography field is successfully obtained. The follow-up work is to perfect the lamellar phase structure, and achieving the ultimate goal that transfers the polymer mask pattern to the wafer substrate. References [1]
[2] [3] [4] [5] [6] [7] [8]
[9] [10]
[11] [12] [13] [14]
[15] [16] [17]
Markoff, J. IBM Discloses Working Version of a Much Higher Capacity Chip. The New York Times; The New York Times Company: New York, July 9 2015; p B2.J. Clerk Maxwell, A Treatise on Electricity and Magnetism, 3rd ed., vol. 2. Oxford: Clarendon, 1892, pp.68–73. A. M. Hawryluk; L. G. Seppala. J. Vac. Sci. Technol. B, 1988, 6, 2162. Gwyn, C. W.; Stulen, R.; Sweeney, D.; Attwood, D. J. Vac. Sci. Technol. B, 1998, 16, 3142-3149. Wagner, C.; Harned, N. Nat. Photonics, 2010, 4, 24−26. Leibler, L. Macromolecules, 1980, 13, 1602. M. Luo, T. H. Epps, Macromolecules 2013, 46, 7567. C. Sinturel, F. S. Bates, M. A. Hillmyer, ACS Macro Lett. 2015, 4, 1044. H. Pathangi, B. T. Chan, H. Bayana, N. Vandenbroeck, D. Van denˈHeuvel, L. Van Look, P. Rincon-Delgadillo, Y. Cao, J. Kim, G. Y. Lin, D. Parnell, K. Nafus, R. Harukawa, I. Chikashi, M. Polli, L. D’Urzo, R. Gronheid, P. Nealey, J. Micro/Nanolithogr. MEMS 2015, 14,031204. G. J. T. Tiddy, Phys. Rep. 1980, 57, 1. J. N. Israelachvili, Intermolecular and Surface Forces with Applications to Colloidal and Biological Systems, Academic Press, Londonˈ1985, pp. 249–257. S. M. Gruner, J. Chem. Phys. 1989, 93, 7562. EKWALLP., in Advances in Liquid Crystal Physics, edited by G. M. BROWN (Academic, New York, N.Y.) 1975. Luckhurst, G. R.; Zannoni, C. Nature, 1977, 267, 412−414. K. Nickmans, J. N. Murphy, B. de Waal, P. Leclère, J. Doise, R. Gronheid, D. J. Broer, A. P. H. J. Schenning, Adv. Mater. 2016, 28, 10068. J. Cattle, P. Bao, J. P. Bramble, R. J. Bushby, S. D. Evans, J. E. Lydon, D. J. Tate, Adv. Funct. Mater. 2013, 23, 5997. P. O. Mouthuy, S. Melinte, Y. H. Geerts, A. M. Jonas, Nano Lett. 2007, 7, 2627. a) C. V. Cerclier, M. Ndao, R. Busselez, R. Lefort, E. Grelet, P. Huber, A. V. Kityk, L. Noirez, A. Schonhals, D. Morineau, J. Phys. Chem. C 2012, 116, 18990; b) R. B. Zhang, X. B. Zeng, B. Kim, R. J. Bushby, K. Shin, P. J. Baker, V. Percec, P. Leowanawat, G. Ungar, ACS Nano 2015, 9, 1759.
Introduction The sustained shrinking of device components is an embodiment of human progress that has led to an explosion of micro- and nanotechnologies. In order to support the rapid development of microelectronics industry, manufacturing process has been developed to the size of 10nm node [1]. In an effort to overcome the size limitations facing top-down microelectronics fabrication , several methods including EUV (extreme ultraviolet)ޔDSA (Directed self-assembly) have been proposed in these years. Extreme ultraviolet (EUV) lithography was first put forward in 1980’s by Hawryluk and Seppala [2]. Gwyn suggested that these extensions are relied on incremental decreases in illumination wavelength and increases in optical numerical aperture (NA) for the system [3]. Extreme ultraviolet lithography (EUVL) based on the industrial optical experience uses 10–14 nm extreme ultraviolet light and is expected to support IC fabrication at 10 nm. Though EUVL has several advantages such as good depth of focus, this technique is still
plagued by large capital investments, source power limitations, resist outgassing complications and its considerable cost [4]. Block copolymer (BCP)-based nanopatterning has paved a strong foundation in nanotechnology including nanoporous membranes, patterned magnetic media, and nanolithography. These materials have attracted much attention because of there excellent self-assembly ability. A previous research of Leibler showed that there were three important physical parameters dictating the self-organizing behavior of di-block copolymers: the Flory−Huggins interaction parameter, χ; the overall degree of polymerization, N; and the polymer composition, expressed as the volume fraction of block A (fA) or block B (fB) [5]. With the view of the Leibler’s theory, many researchers are inclined to focus di-block copolymers that have high χ and low N. Unfortunately, an immiscibility-driven approach will not suffice when sub-5 nm periodicities are desired, preventing extendibility to smaller dimensions. In addition, although the assembly of block copolymers can be directed within a photolithographic prepattern, the formation of defect-free periodic structures remains a challenge. [6-8]. Lyotropic liquid crystal (LLC) mesogens are amphiphilic molecules containing a hydrophobic organic tail section and a hydrophilic headgroup [9-10]. Depending on the overall shape and the interfacial curvature energy of the system, monodisperse aqueous domains ranging in structure from lamellae to cylindrical channels with dimensions in the 1–10 nm size range can be formed [11]. As early as 1975Ekwallp has put forward that the smectic phase formed by lyotropic liquid crystals is a lamellar structure with periodically repeated surfactant layers [12].liquid crystalline ordering suggests the possibility of long-ranged pattern formation with very small resolution and few defects, which can’t get from di-block polymers [13].These special materials have the advantage that they can be easily aligned into defect free and sub-5 nm patterns [14]. Exciting work has been performed on the confinement of liquid crystals in structures such as microchannels,[15] nanogrooves,[16] or nanopores,[17] but the directed self-assembly of thin films with sub-5 nm periodicities has not been reported. Therefore, this study synthesized some kinds of polymerizable liquid crystal molecule to form the target lamellar template with photolithography value, which could also provide a new idea for the design and construction of lithography materials. Experiment and discussion In this study, we synthesized a kind of polymerizable LLC
molecule, the synthetic route and molecule structure are shown in Fig.1. The structure has been confirmed by NMR, 1H NMR (400 MHz, d5-methanol): ¥7.27 (s, 2H), 5.82 (dd, 3H),5.03 (dd, 3H), 4.96 (dd, 3H), 4.08 (t, 6H), 3.95 (t, 6H), 1.52 (m, 56 H). Then we mixed the LLC molecule with appropriate amount of water to form ordered structure at the same time explore the impact of water. The effect of different water contents has been studied. When the LLC monomer content is 80%, the target lamellar phase can be obtained, as shown in Fig.2. When the LLC monomer content is lower, a mixed structure occurs, in which we guess it exists lamellar and hexagonal structure simultaneously. With the reduction of water content, lamellar is disappeared while hexagonal is appeared, as shown in Fig.3. Since the monomer has three double bonds, after crosslinking the original ordered structure can be maintained. The crosslinking process needs photoinitiator and a UV light source with a wavelength of 365nm. Then after some specific processing, the polymer free-standing film is able to have the potential value as a mask that can be applied in the lithography field. In the next step, we will try to introduce this LLC molecule into a prepared template made by EBM to explore its further application, which may be not only limited in the lithography field.
Fig. 2 (a) SAXS profile of 80% LLC monomer
Fig. 2 (b) POM image of 80% LLC monomer
Fig. 1 (a) LLC Monomer synthetic route
Fig. 2 When the LLC monomer content is 80%, the lamellar structure is obtained, as shown by the SAXS(a) and POM results(b).
Fig. 1 (b) NMR result of the final product. Fig. 1 LLC Monomer synthetic route (a) and NMR result of the final product (b).
Fig. 3 When the LLC monomer content is 60%, the hexagonal structure is obtained, as shown by the SAXS result.
Conclusions
Through the multi-step synthesis, a liquid crystal molecule with polymerization ability is successfully obtained. After adjusting the concentration of deionized water and crosslinking, the polymer mask with lamellar structure which has value being used in lithography field is successfully obtained. The follow-up work is to perfect the lamellar phase structure, and achieving the ultimate goal that transfers the polymer mask pattern to the wafer substrate. References [1]
[2] [3] [4] [5] [6] [7] [8]
[9] [10]
[11] [12] [13] [14]
[15] [16] [17]
Markoff, J. IBM Discloses Working Version of a Much Higher Capacity Chip. The New York Times; The New York Times Company: New York, July 9 2015; p B2.J. Clerk Maxwell, A Treatise on Electricity and Magnetism, 3rd ed., vol. 2. Oxford: Clarendon, 1892, pp.68–73. A. M. Hawryluk; L. G. Seppala. J. Vac. Sci. Technol. B, 1988, 6, 2162. Gwyn, C. W.; Stulen, R.; Sweeney, D.; Attwood, D. J. Vac. Sci. Technol. B, 1998, 16, 3142-3149. Wagner, C.; Harned, N. Nat. Photonics, 2010, 4, 24−26. Leibler, L. Macromolecules, 1980, 13, 1602. M. Luo, T. H. Epps, Macromolecules 2013, 46, 7567. C. Sinturel, F. S. Bates, M. A. Hillmyer, ACS Macro Lett. 2015, 4, 1044. H. Pathangi, B. T. Chan, H. Bayana, N. Vandenbroeck, D. Van denˈHeuvel, L. Van Look, P. Rincon-Delgadillo, Y. Cao, J. Kim, G. Y. Lin, D. Parnell, K. Nafus, R. Harukawa, I. Chikashi, M. Polli, L. D’Urzo, R. Gronheid, P. Nealey, J. Micro/Nanolithogr. MEMS 2015, 14,031204. G. J. T. Tiddy, Phys. Rep. 1980, 57, 1. J. N. Israelachvili, Intermolecular and Surface Forces with Applications to Colloidal and Biological Systems, Academic Press, Londonˈ1985, pp. 249–257. S. M. Gruner, J. Chem. Phys. 1989, 93, 7562. EKWALLP., in Advances in Liquid Crystal Physics, edited by G. M. BROWN (Academic, New York, N.Y.) 1975. Luckhurst, G. R.; Zannoni, C. Nature, 1977, 267, 412−414. K. Nickmans, J. N. Murphy, B. de Waal, P. Leclère, J. Doise, R. Gronheid, D. J. Broer, A. P. H. J. Schenning, Adv. Mater. 2016, 28, 10068. J. Cattle, P. Bao, J. P. Bramble, R. J. Bushby, S. D. Evans, J. E. Lydon, D. J. Tate, Adv. Funct. Mater. 2013, 23, 5997. P. O. Mouthuy, S. Melinte, Y. H. Geerts, A. M. Jonas, Nano Lett. 2007, 7, 2627. a) C. V. Cerclier, M. Ndao, R. Busselez, R. Lefort, E. Grelet, P. Huber, A. V. Kityk, L. Noirez, A. Schonhals, D. Morineau, J. Phys. Chem. C 2012, 116, 18990; b) R. B. Zhang, X. B. Zeng, B. Kim, R. J. Bushby, K. Shin, P. J. Baker, V. Percec, P. Leowanawat, G. Ungar, ACS Nano 2015, 9, 1759.