Nanoimprint Lithography

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1. Nanoimprint Lithography By Debendra Timsina Department of Physics and Material Science University of Memphis 1 Nanoimprint Lithography

2. Outlines History Introduction Types of NIL Applications Prospects and Challenges Conclusion 2 Nanoimprint Lithography

3. History As early as 500 BC , there is evidence of carved characters in stone and ceramic. Johannes Gutenberg is generally credited with the invention of modern printing Historically hot embossing technique was using for many purpose in the large scale. 3 Nanoimprint Lithography

4. Introduction Nanoimprint Lithography (NIL) first used by Prof Stephen Chou and his students in scientific community in 1996. NIL is simple cost-effective, high throughput and high-resolution process. NIL able to get high resolution feature size up to 2 nm with high throughput. 4 Nanoimprint Lithography

5. Principle of NIL NIL works on the principle of mechanical deformation of resists using mold containing nanostructure during heat or UV curing process. M old or template is generally prepared by E-beam lithography. Materials used like Si, SiO2, Quartz, Ni Thermoplastic or UV curable resist are used. Pattern transferred by anisotropic etching to remove residue resist. 5 Nanoimprint Lithography

6. Two Fundamentals Types of NIL Thermal NIL Step 1 :Resist coating Stamp materials: Si, SiO2, Opaque Resist: Thermoplastic Polymer (PMMA) Viscosity: 10 3 - 10 7 Pa S Step 2 : Heat & Press Temperature:100-200°C > T g Pressure:20-100 bar Step 3 : Cool and Separate Demold T: 20-80 °C UV- NIL Step 1 : Resist Coating Stamp materials: Glass, SiO 2 transparent. Resist: Liquid photopolymer (SU-8) Viscosity: 10 -2 - 10 -3 Pa S Step 2 : Press & UV Expose Temperature: 20 °C (RT) Pressure 0-5 bar Step 3 : Separate Demold T: 20 °C (RT) 6 Nanoimprint Lithography Both thermal and UV-NIL have demonstrated a sub-10 nm resolution.

7. Other Types of NIL Hard UV-NIL Hard mold; quartz glass releasing agent required surface waviness limit imprint area Difficult to insure uniform and parallel surface contact Soft UV-NIL Soft mild like PDMS No conglutination High pattern transferring area High pression feature Reduce parallelism error between mold and substrate But resolution limitation and non uniformity 7 Nanoimprint Lithography Types of UV-NIL

8. 8 Nanoimprint Lithography Combination of UV and Thermal NIL Thermal expansion mismatch between stamp and substrate are avoided

9. Reverse NIL Spin-coated onto the mold rather than substrate Mold has low surface energy than substrate Able to construct 3-D and Multilayer micro/nano structure. 9 Nanoimprint Lithography

10. Jet and Flash Imprint Lithography 10 Nanoimprint Lithography Able to imprint in large depressed surface and thick film

11. Laser Assisted NIL 11 Nanoimprint Lithography Used to make nano structure in Si and metal. Rapid process Doesn’t required etching Resolution better than 10 nm Can be used for large area pattern (a whole wafer)

12. Roll Imprint Process (RNIL) Advantages Continues process High Throughput Low cost Low energy Simple system construction 12 Nanoimprint Lithography Steps Deposition Patterning Packaging

13. 13 Nanoimprint Lithography RNIL: Mold Type Two Method of RNIL Roller Mold Flat Mold and smooth Roller

14. Two Substate Type Flexible Rigid 14 Nanoimprint Lithography RNIL: Substrates Type

15. 15 Nanoimprint Lithography Nanoelectrode Lithography Combine nanoimprint with electrochemical reaction The conductive mold pattern undergoes an electrochemical reaction that enables an oxide pattern to be fabricated directly on the surface of a semiconductor or metal layer. Resistless and multiple patterning will improve accuracy and flexibility

16. 16 Nanoimprint Lithography Dynamic Nanoscribing Lithography Creates continuous structures over substrates of any length DNI can be applied to many polymer films and the resulting pattern profile can be controlled by the localized heating. DNI enables continuous patterning on flat or curved surfaces and can follow circular or bent path as well

17. 17 Nanoimprint Lithography Dynamic Nanoscribing (DNI) Laser Assisted Direct Imprint (LADI) Nanoimprint Lithography Variant Based on Resist curing Unconventional Imprint Roll-to-Roll Conventional Imprint Variant Based on Mold Type Variant Based on Contact Method Thermal UV Plate-to-Plate Roll-to-Plate Hard Mold Imprint Soft Mold Imprint Functional Resin Imprint Nanoelectrode Lithography (NEL) Classifications of NIL

18. Application of NIL NIL technique used to make Memory devices: HDD, NAND flash memory Optical Storage Device :HD-DVD, Blue-Ray High Brightness LED, OLED, LCD, field emission display, organic light emitting display Optical elements : Lens, diffractive grating, waveguide, tunable optical filter, nano wire grid polarizer Biological devices: Biosensors, Biomedicine, Nanofluidic devices, microarrays for genomics, proteomics and tissue engineering, nanoscale protein patterning 18 Nanoimprint Lithography

19. Nanoelectronics: molecular electronics, AFM tips High-end semiconductors and high-density interconnects, other NEMS/MEMS applications: solar cell, fuse cell, CNT sensor, etc. Manufacturing of metasurfaces which has application in optical communicating, sensing, energy harvesting etc. 3-D printing, multi layer nano channels 19 Nanoimprint Lithography Application of NIL

20. Applications of NIL 20 Nanoimprint Lithography

21. Prospects and Challenges Prospects High resolution : NIL has the potential to achieve sub-10 nm resolution, which is essential for many nanofabrication applications in electronics, optics, and biotechnology. Scalability : NIL can be easily scaled up to produce large-area patterns, making it suitable for industrial-scale manufacturing. 21 Nanoimprint Lithography

22. Prospects and Challenges Prospects Low cost : NIL has lower equipment and operating costs compared to other lithographic techniques, such as electron beam lithography, which makes it more accessible to small and medium-sized enterprises. Versatility : NIL can be used to pattern a wide range of materials, including polymers, metals, and ceramics, making it a versatile technique for various applications. 22 Nanoimprint Lithography

23. Prospects and Challenges Challenges Template fabrication : The fabrication of high-quality templates or molds with sub-10 nm resolution is challenging and time-consuming. The cost of the templates can also be high, especially for high-resolution patterns. Material properties : The choice of resist material is critical for achieving high-resolution patterns using NIL. However, not all materials are suitable for NIL, and some may exhibit unwanted properties, such as shrinkage or cracking. Alignment: The alignment of the template with the substrate is critical for achieving high-resolution patterns. However, misalignment can occur, leading to defects in the pattern. 23 Nanoimprint Lithography

24. Prospects and Challenges Challenges Large-area patterning : Although NIL can be easily scaled up to produce large-area patterns, the uniformity and consistency of the patterns can be challenging to achieve over large areas. Integration with other techniques: NIL may need to be integrated with other lithographic techniques, such as electron beam lithography or photolithography, to achieve even higher resolution patterns or more complex device structures. However, the integration of these techniques can be challenging and may require additional processing steps 24 Nanoimprint Lithography

25. Conclusion In conclusion, Nanoimprint lithography (NIL) is a promising nanofabrication technique that can produce high-resolution patterns with low cost and high throughput. Recent advances in NIL have further improved its performance and capabilities, including the development of high-resolution templates, advanced resist materials, soft imprint lithography, roll-to-roll NIL, and hybrid imprint lithography. However, NIL still faces several challenges, including template fabrication, material properties, alignment, large-area patterning, and integration with other lithographic techniques. Despite the challenges, the potential benefits of NIL make it an exciting technology with many promising applications in electronics, optics, and biotechnology. 25 Nanoimprint Lithography

26. References Lan H , Ding Y . Nanoimprint Lithography. In: Lithography . InTech . Resnick D . Nanoimprint lithography. In: Nanolithography: The Art of Fabricating Nanoelectronic and Nanophotonic Devices and Systems . Elsevier Ltd, 2013, p. 315–347. Chou S. Nanoimprint lithography. Technol Rev 106: 42, 2003. Chou SY , Krauss PR , Renstrom PJ . Imprint of sub-25 nm vias and trenches in polymers. Appl Phys Lett 67: 3114, 1995. doi : 10.1063/1.114851. Hua F , Sun Y , Gaur A , Meitl MA , Bilhaut L , Rotkina L , Wang J , Geil P , Shim M , Rogers JA , Shim A . Polymer imprint lithography with molecular-scale resolution. Nano Lett 4: 2467–2471, 2004. doi : 10.1021/nl048355u. Handrea -Dragan M , Botiz I . Multifunctional structured platforms: From patterning of polymer-based films to their subsequent filling with various nanomaterials. Polymers (Basel) 13 MDPI AG: 1–49, 2021 Higashiki T . Nanoimprint lithography and future patterning for semiconductor devices. Journal of Micro/Nanolithography, MEMS, and MOEMS 10: 043008, 2011. doi : 10.1117/1.3658024. Nanoimprint Lithography – YouTube Kehagias N , Reboud V , Chansin G , Zelsmann M , Jeppesen C , Reuther F , Schuster C , Kubenz M , Gruetzner G , Sotomayor Torres CM . Submicron three-dimensional structures fabricated by reverse contact UV nanoimprint lithography. Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures 24: 3002, 2006. doi : 10.1116/1.2388962. Colburn M , Grot A , Amistoso MN , Choi BJ , Bailey TC , Ekerdt JG , Sreenivasan S V. , Hollenhorst J , Willson CG . Step and flash imprint lithography for sub-100-nm patterning. In: Emerging Lithographic Technologies IV . SPIE, 2000, p. 453–457. Han KS , Hong SH , Lee H . Fabrication of complex nanoscale structures on various substrates. Appl Phys Lett 91, 2007. doi : 10.1063/1.2789735. Chou SY , Keimel C , Gu J . Ultrafast and direct imprint of nanostructures in silicon. Nature 417: 835–837, 2002. doi : 10.1038/nature00792. Lee T , Lee C , Oh DK , Badloe T , Ok JG , Rho J . Scalable and high-throughput top-down manufacturing of optical metasurfaces . Sensors (Switzerland) 20 MDPI AG: 1–33, 2020. Yokoo A , Namatsu H . NTT Technical Review [Online]. https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr200808sp3.pdf&mode=show_pdf 26 Nanoimprint Lithography

27. Thank You! 27 Nanoimprint Lithography