Etching of sub-micrometer structures through Stencil G. Villanueva , O. Vazquez-Mena, M.A.F. van den Boogaart, K. Sidler, V. Savu and J. Brugger Microsystems Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL) CH-1015 Lausanne, Switzerland phone: +41–21–6937818 e-mail: Guillermo.Villanueva@epfl.ch , Juergen.Brugger@epfl.ch Keywords: Shadow mask, Stencil, Reactive Ion Etching (RIE) ABSTRACT INTRODUCTION The processing techniques for micro and nano devices fabrication can be divided into two groups. On one hand, there are the techniques that allow the modification of a given substrate, e.g. ionic implantation, metallization, etching and thermal processes to either grow or deposit insulator layers. On the other hand, there are the processes that allow a pattern transfer of the designs onto the substrate. The general name for this second kind of processes would be lithography, including optical lithography, electron beam lithography (EBL), ion beam lithography (IBL), nanoimprint lithopraphy (NIL) and stencil lithography (SL) among others. The actual fabrication of micro and nano devices consists in the pattern transfer of designs onto a substrate, which means that a combination of both types of processes must be used. The majority of the lithographic methods mentioned before rely on the use of pre-patterned resists that selectively expose certain parts of the substrate either to a material deposition or to an etching process. Those resists are organic compounds which imply their coating, exposure, development and removal. In addition, their use also imposes certain restrictions regarding the materials and substrates to pattern. In this sense, as it is necessary to use solvents or O 2 plasma to remove the resists and it is necessary to place the substrate at relatively high temperatures (around 100-200ºC), not all the substrates can be processed using resists. Alternatively, it is possible to use resistless process as Stencil Lithography that widen the different types substrates that can be used and leads to a reduction in the number of steps in the fabrication process flow. Stencil Lithography has been widely used in the last years to locally deposit metals on a substrate, providing sub-micrometer resolution [1, 2]. The deposited metals can be used either to create contacts [3], to fabricate a mechanical system [4] or to act as a mask for the posterior etching of the substrate [5, 6]. Although this technique has mainly been used for the selective deposition of metal, it has also been used to perform ionic implantation [7] and etching [8-10]. In this work, the experiments performed when using stencils as a hard mask for dry etching of thin films are presented. Therefore, the exceptional work performed by Pang et al. [11] on GaAs, has been extended into silicon, polycrystalline silicon, silicon dioxide, silicon nitride and polyimide.