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Muhammad M.,University of Alberta | Muhammad M.,Canadian National Institute For Nanotechnology | Buswell S.C.,Applied Nanotools Inc. | Dew S.K.,University of Alberta | And 2 more authors.
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2011

As a low cost and high throughput method for nanoscale pattern replication, step and flash imprint lithography (SFIL) with UV transparent masters is gaining prominence for its potential in photonics and integrated-circuit fabrication. However, dielectric materials appropriate for fabricating nanostructured SFIL masters present a challenge when employing electron beam lithography (EBL) because insulator substrates covered by polymeric resists such as PMMA tend to accumulate charge during EBL exposures, thereby degrading the process. In this work we explore the performance of four different EBL anticharging schemes for nanofabrication of dense arrays of dots having diameters 16-30 nm in PMMA on UV transparent fused silica (FS) substrates. These include overlayers of aluminum or a water-soluble conducting polymer, as well as sandwiching of Al or Cr thin films between the substrate and PMMA. The quality of patterns transferred from PMMA into the underlying metallic layers was analyzed, and the grain size of the metal was found to be the limiting factor determining the edge roughness. The best resolution was attained employing the conducting polymer top-coating. This scheme also involves fewer processing steps. The authors have used this technique for lift-off of Cr and Au as well as Cr masked etch transfer of nanosized patterns into glass substrates for UV-transparent master mold fabrication. © 2011 American Vacuum Society. Source


Stepanova M.,Canadian National Institute For Nanotechnology | Fito T.,Canadian National Institute For Nanotechnology | Fito T.,University of Alberta | Szabo Z.,Canadian National Institute For Nanotechnology | And 8 more authors.
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2010

The authors report a numeric simulation tool that they developed for the modeling and analysis of electron beam lithography (EBL) of nanostructures employing a popular positive tone resist polymethylmethacrylate (PMMA). Modeling and process design for EBL fabrication of 5-50 nm PMMA structures on solid substrates is the target purpose of the simulator. The simulator is functional for exposure energies from 1 to 50 keV with arbitrary writing geometries. The authors employ a suite of kinetic models for the traveling of primary, secondary, and backscattered electrons in the resist, compute three-dimensional (3D) distributions of the yield of main-chain scission in PMMA, and convert these into the local volume fractions of fragments of various sizes. The kinetic process of development is described by the movement of the resist-developer interface with the rate derived from the mean-field theory of polymer diffusion. The EBL simulator allows the computation of detailed 3D distributions of the yield of main-chain scission in PMMA for various conditions of exposure, the corresponding volume fractions of small fragments, and the clearance profiles as functions of the development in time and temperature. This article describes the models employed to simulate the EBL exposure and development, reports examples of the computations, and presents comparisons of the predicted development profiles with experimental cross-sectional resist profiles in dense gratings. © 2010 American Vacuum Society. Source


Mohammad M.A.,University of Alberta | Fito T.,University of Alberta | Fito T.,Canadian National Institute For Nanotechnology | Chen J.,Canadian National Institute For Nanotechnology | And 3 more authors.
Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures | Year: 2010

The authors report a systematic experimental study of dense nanostructures in polymethylmethacrylate (PMMA) created by low-energy electron beam lithography (EBL) with varying duration and temperature of the resist dissolution. They observe that decreasing the development temperature not only yields the widest favorable exposure dose regimes but also requires highest exposure doses to fabricate dense nanopatterns. They interpret the observed interdependence of the exposure doses and the development temperatures in terms of a simple kinetic model describing the diffusion mobility of fragments in exposed PMMA during dissolution and discuss the corresponding molecular mechanisms that determine the resolution and sensitivity of EBL nanofabrication. © 2010 American Vacuum Society. Source


Horvath C.,Applied Nanotools Inc. | Bachman D.,University of Alberta | Mi G.,University of Alberta | Van V.,University of Alberta
IEEE Photonics Technology Letters | Year: 2015

We report a simple and robust method for fabricating graphene-on-silicon waveguides on a silicon-on-insulator (SOI) chip. The waveguide consists of a silicon core covered by a graphene layer whose width exactly conforms with the width of the silicon core and whose length can be precisely controlled. Raman spectroscopy showed that the graphene layer retained its high quality after processing. Transmission measurements of fabricated graphene-on-silicon waveguides showed polarization-dependent propagation losses of 0.03 dB/ μm for the transverse-electric (TE) mode and 0.07 dB/μm for the transverse-magnetic (TM) mode, in excellent agreement with theoretical simulations. © 2015 IEEE. Source


Horvath C.,Applied Nanotools Inc. | Bachman D.,University of Alberta | Van V.,University of Alberta
IEEE International Conference on Group IV Photonics GFP | Year: 2014

We demonstrated a method for fabricating edge-conformed silicon-graphene waveguides on an SOI chip. Transmission measurements showed large waveguide attenuation of 0.1dB/μm for TM and 0.036dB/μm for TE mode due to strong optical absorption of graphene. © 2014 IEEE. Source

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