Rainer Schöftner

Fabrication of 3D-photonic crystals via UV-nanoimprint lithography

Optical lithography will reach its limits due to the diffraction effects encountered and the necessity for using complex resolution enhancement techniques like optical proximity correction, phase shift masks, and off-axis illumination [L. W. Liebmann et al., in Advanced Semiconductor Lithography (2001), Vol. 45]. The restrictions on wavelength, in combination with high process and equipment costs, make low-cost, simple imprinting techniques competitive with next-generation lithography methods. There are several nanoimprint lithography (NIL) techniques which can be categorized depending on the process parameters and the imprinting method—either step and repeat or full wafer single-step imprinting. A variety of potential applications has been demonstrated using NIL (e.g., surface acoustic wave devices, vias and contact layers with dual damascene imprinting process, Bragg structures, patterned media) [M. D. Stewart et al., Proc. SPIE 5751, 210 (2005); P. Dorsey et al., in Discrete Track Recording (DTR) Media...

Covalent immobilisation of protease and laccase substrates onto siloxanes

Immobilisation of enzyme substrates is a powerful tool in the detection of enzymes in the chemosphere and the environment. A siloxane based strategy for the covalent immobilisation of oxidoreductase and protease substrates was developed involving activation of silica gel and polyethylene terephthalate (PET) as model carriers with (3-aminopropyl)-triethoxysilane or (3-mercaptopropyl)-trimethoxysilane (APTS, MPTS). Ferulic acid and L-Leucine-p-nitroanilide, Gly-Phe p-nitroanilide (GPpNA) and N-Succinyl-Ala-Ala-Pro-Leu p-nitroanilide (SAAPLpNA) as laccase and protein substrates, respectively, were covalently attached using glutaraldehyde or carbodiimide based cross-linking strategies. In contrast to conversion in solution, immobilised SAAPLpNA was hydrolysed much faster by protease than immobilised GPpNA indicating steric hindrance with decreasing chain length between point of attachment and site of enzyme attack. Immobilised ferulic acid was oxidised by laccase both in case of MPTS and APTS-modified silica gel giving clearly visible colour changes with Delta E values of 7.2 and 2.3, respectively after 24h of incubation, where Delta E describes the distance between two colours. Similarly, clearly visible colour changes with a Delta E value of 8.6 were seen after laccase treatment of ferulic acid immobilised on APTS activated PET as carrier. Limited surface hydrolysis of PET with a cutinase enhanced coupling of APTS and ferulic acid due to a larger number of hydroxyl groups available on the surface and consequently led to a higher colour difference of Delta E=12.2 after laccase oxidation. The covalent coupling product between ferulic acid and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was identified by LC-MS (M+1m/z601) and successfully oxidised with laccase.

Nanoimprint activities in Austria in the research project cluster NILaustria

The NILaustria research project cluster consists of 8 individual research projects and aims to improve nanoimprint lithography in an application driven approach. The cluster is presented as well as highlights from the projects, e.g. the replication of 12.5nm half pitch features using working stamp copies, topics from organic electronics, metamaterials and SiGe technology. An outlook on the new activities is given.

Effects of a compliant layer in solid parallel-plate UV-based nanoimprint lithography

We deal with solid parallel-plate UV-based nanoimprint lithography (UV-NIL) using rigid quartz stamps and spin coated substrates. Achieving homogeneous imprints with a thin residual layer are important for a succeeding reactive ion etching (RIE) step. Since the solid stamp and the substrate are not perfectly flat and mounted on solid parallel plates giving them little chance to adapt and compensate for the unevenness and causing additional distortions, this is difficult to achieve. We investigated the bending of a rigid quartz stamp during imprinting and the effect of a thin compliant layer located below the substrate with finite element simulations and compared them with experimental results. We show that a close contact of stamp and substrate can be achieved with a correctly designed compliant layer and using a commercially available EVG®620 mask aligner.

Fabrication process of 3D-photonic crystals via UV-nanoimprint lithography

In recent years the standard lithography reached its limits due to the diffraction effects encountered and the necessary complexity of compatible masks and projection optics. The restrictions on wavelength, in combination with high process and equipment costs make low cost, simple imprinting techniques competitive with next generation lithography methods. There are several Nanoimprint Lithography (NIL) techniques which can be categorized depending on the process parameters and the imprinting method - either step & repeat or full wafer imprinting. A variety of potential applications has been demonstrated using NIL (e.g. SAW devices, vias and contact layers with dual damascene imprinting process, Bragg structures, patterned media) [1,2]. In this work UV-NIL has been selected for the fabrication process of 3D-photonic crystals. Results with up to three layers will be demonstrated.