HSQ resist for replication stamp in polymers M. R. Saleem a,c, *, P. A. Stenberg a , M. B. Khan c , Z. M. Khan c , S. Honkanen a,b , J. Turunen a a University of Eastern Finland, Department of Physics and Mathematics, P. O. Box 111, FIN-80101 Joensuu, Finland. b Department of Micro and Nanosciences, Aalto University, P.O. Box 13500, FI-02015 TKK, Helsinki, Finland. c National University of Sciences and Technology (NUST), School of Chemical and Materials Engineering (SCME), Sector H-12, Islamabad, Pakistan. * Corresponding author: (Tel) +358 13 251 3212, (Fax) +358 13 251 2721 E-mail: rizwan.saleem@uef.fi , Rizwanphy@gmail.com ABSTRACT We investigated an affordable, accurate and large scale production method to fabricate sub-wavelength grating structures by replication in polycarbonate substrates by hot embossing. We used hydrogen silsesquioxane (HSQ) a high resolution, binary, inorganic, negative electron beam resist, on silicon substrate to make a stamp for replication. We fabricated the stamp on silicon by using HSQ-resist without any etching process with simple process steps. The process starts by depositing an HSQ-resist layer on a silicon substrate and by a measurement of the desired film thickness by adjusting the spinning speed and time. The resist material is then subjected to e-beam writing followed by a heat treatment to enhance the hardness and to reveal properties analogous to solid SiO 2 as a hot embossing stamp material. A comparison study is made with and without the etching process with different etching rates. We demonstrate that an effective and inexpensive stamp for thermal nano-imprint lithography (NIL) for optical gratings is provided without an etching process, which gives a uniform imprinting density over the entire grating surface and high imprint fidelity. The reflectance spectra of replicated grating structures are also shown to be in agreement with theoretical calculations. Key words: HSQ, nano-imprint lithography, sub-wavelength gratings, nano-scale devices. 1. Introduction The replication technology by nano-imprint lithography (NIL) in transparent polymer materials is highly promising for advanced photonic applications. For example, the replicated guided mode resonance filters (GMRFs) with well- defined nanometer dimensions (linewidth and height) are important as sensors 1 . It has already been shown that periodic grating structures can be replicated in polycarbonate for potential photonic applications 2 . The diffractive optical elements (DOEs) consist of periodic micro reliefs with features ranging from sub-wavelength dimensions upward from less than micrometer to tens of microns. Polymer materials are strong candidates for DOEs, to be fabricated by employing various replication techniques such as hot embossing, injection molding etc. 3,4 . The properties of the stamping material are very important to achieve a well featured replication and act as the limiting step. Generally, the patterns are defined to a resist material on silicon substrate by electron beam lithography (EBL), followed by reactive ion etching of the substrate material. Stamp fabrication by this process requires a high resolution resist with complete control over the etching process, such as etching rate, gas flows, pressure etc. The complete control of the pattern depth is a difficult step and can cause a variation in depth for different linewidth structures. The proximity effect becomes more significant with the increase of the complexity of pattern shape in EBL. The fluctuations become more significant as the beam size becomes comparable to the pattern size. An additional Advanced Fabrication Technologies for Micro/Nano Optics and Photonics V, edited by Winston V. Schoenfeld, Raymond C. Rumpf, Georg von Freymann, Proc. of SPIE Vol. 8249, 82490G · © 2012 SPIE CCC code: 0277-786X/12/$18 · doi: 10.1117/12.907862 Proc. of SPIE Vol. 8249 82490G-1 Downloaded from SPIE Digital Library on 17 Feb 2012 to 130.233.148.75. Terms of Use: http://spiedl.org/terms