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UV-Curved Nano Imprint Lithography

UV-Curved Nano Imprint Lithography. Lithography Imprint-To produce (a mark or pattern) on a surface by pressure . Nanoscale Uv - Method. Introduction. This was first invented by Prof. Stephen Chou and his students in 1995. This is a method of fabricating nanometer scale patterns.

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UV-Curved Nano Imprint Lithography

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  1. UV-Curved Nano Imprint Lithography

  2. Lithography • Imprint-To produce (a mark or pattern) on a surface by pressure. • Nanoscale • Uv- Method

  3. Introduction • This was first invented by Prof. Stephen Chou and his students in 1995. • This is a method of fabricating nanometer scale patterns. • It creates patterns by mechanical deformation of imprint resist and subsequent processes. • This is the road map for the 32-nm semiconductor technology

  4. Requirements • The materials required for the Imprint technique is • (i) a mold with predefined surface relief nanostructures, and • (ii) a suitable resist material that can be deformed and hardened to preserve the shape of the impression.

  5. Mold Fabrication • Thermal expansion co-efficient is an important factor to be considered. • Si, SiO2, SiC, silicon nitride, metals,sapphire, and diamond film.

  6. Steps in fabrication:- • A resist material is spin-coated onto the mold surface. • Followed by lithography to define the desired mold pattern. • A hard masking layer, such as a metal can be deposited over the patterned resist template. • Followed by a lift-off process that removes the resist template and the material on top, leaving a patterned mask layer on the Si substrate. • An anisotropic RIE process is used to selectively etch away the Si material in the unmasked region, producing the surface relief structures required for NIL

  7. Types • Thermoplastic Nanoimprint lithography • Uv-curved NanoImprintLithographhy • Roll imprint process, • Laser-assisted direct imprint, • Reverse imprint lithography, • Substrate conformalimprintlithography, • Ultrasonic NIL, etc.

  8. Uv-Curved Method • The UV curved Nanoimprint Lithography is normally carried out in room temperature and at low pressure. • The mold material used is of transparent type fused with silica. • Here we do use the soft UVfor the lithographic process. • The resist material used is the liquid polymer but in thermal method they use thermal plastic.

  9. Principle:- • The transparent mold is pressed over the resist material. • Now the cavities are fully filled by the resist. • Now the resist is curved by the UV-rays so that the resist will become solid and it is etched till the base. • After demolding, a similar pattern transfer process can be used to transfer the pattern in resist onto the underneath material

  10. Crucial process issues for NIL • Thickness and uniformity of residual layer.. • Pattern fidelity(Precision) • Defect control • Filling process

  11. Key concern for NIL templates • Template surface treatment • Defect inspection. • Lifetime.

  12. Advantages • Nanoimprint lithography has experimentally been shown to achieve 25nm feature size . • The promise of repeatability and durability consequently leads this to low costs and ease of fabrication.

  13. DrawBacks • The surface sticking problem has not been perfected . • The molding conditions haven’t been optimized . • The effect of thermal expansion through the process is not fully understood.

  14. Applications • Nanoimprint lithography has been used to fabricate devices for electrical, optical, photonic and biological application. • For electronics devices, NIL has been used to fabricate MOSFET, O-TFT, single electron memory. For optics and photonics, intensive study has been conducted in fabrication of subwavelength resonant grating filter, polarizers, waveplate, anti-reflective structures, integrated photonics circuit and plasmontic devices by NIL.

  15. The future of nanoimprint • Nanoimprint lithography is a simple pattern transfer process that is neither limited by diffraction nor scattering effects nor secondary electrons, and does not require any sophisticated radiation chemistry. It is also a potentially simple and inexpensive technique. • However, a lingering barrier to nanometer-scale patterning is the current reliance on other lithography techniques to generate the template. • As of October 2007, Toshiba is the only company to have validated nanoimprint lithography for 22 nm and beyond.

  16. Reference • S. Chou, P. Krauss, P. Renstrom, 1996, “Nanoimprint lithography,” J. Vac. Sci. Technol. B, Volume 14(6), pp. 4129-4133. • S. Chou, P. Krauss, P. Renstrom, 1996, “Imprint Lithography with 25-Nanometer Resolution,” SCIENCE, Volume 272, pp. 85-87. • www.wikipedeia.org

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