Optoelectronics Research Centre Tampere University of Technology

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Nanoimprint Lithography for Fabrication of Nanophotonic Components

  Technology Description

Microelectronics and integrated optics require fabrication techniques which are able to replicate patterns in sub-micron scale with low cost of ownership. Recent observations indicate that Nanoimprint Lithography (NIL) may become a technique suitable for next-generation nano-patterning applications. We are developing NIL for fabrication of nanophotonic components including photonic crystals, diffraction gratings, nanopatterned surfaces for epitaxial semiconductor growth and metal surface reliefs.

Applications / use-cases:

Nanopatterning supported growth
Nanopatterning supported growth allows lattice mismatched growth of dislocation free layers and ordered arrays of quantum dots with uniform size. NIL is ideal method to pattern the semiconductor wafers before growth.

Plasmonics
Surface plasmons in thin metal films enable manipulation of light in dimensions well below the optical wavelength, thus breaking the diffraction limit hindering the miniaturization of optical devices. By combining the metal nanostructures having sub-wavelength surface corrugation with materials that provide optical gain we not only overcome the absorption losses, but also strengthen emission. Surface plasmons have already been used to improve the output power of VCSELs and resonating modes of quantum cascade lasers at the far-IR. Plasmonics play a key role in this emerging field of science and technology, which is only beginning to see its first applications.

Photonic crystals
Photonic crystals are multidimensional periodic structures with period in order of a wavelength of light. They form a wavelength range (photonic band gap) where light can't propagate and electrons can't emit photons. The future applications include miniature light emitters and compact integrated optics.

Advantages over current alternatives:

This lithography technique allows for solid surfaces to be structured on a nanometre scale. A nano-patterned master needs first to be prepared by another method, e.g., by electron beam lithography (EBL). From the master plate, NIL stamps are replicated. Each stamp can be used hundreds of times to imprint surface reliefs, opening up many new applications that are not affordable by EBL. The stamp replication reduces the processing time and cost by a factor of 100, making UV-NIL very attractive for volume production of functional surface nanostructures.
An additional attractive point of NIL is the fact that it is compatible to conventional photo lithographic processes.

Advantages of Nanoimprint Lithography:

• Single master plate can be replicated potentially hundreds of times
• Large area per imprint step
• Feature size below 10 nm is achievable
• Fast wafer scale patterning
• Relatively low capital investment to lithography equipment

Seeking partnerships for:

Commercialization:	Finding applications and users for low cost nanostructure fabrication on semiconductors and optical fibers
Joint technology development:	Development of materials for UV-NIL (Soft stamp materials, Resists) Fabrication of NIL masters by e-beam or other conventional lithography Designing nanostructures for fabrication of advanced optoelectronics components

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