Post-CMOS Integration of Nanomechanical Devices by Direct Ion Beam Irradiation of Silicon
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Post-CMOS Integration of Nanomechanical Devices by Direct Ion Beam Irradiation of Silicon
Francesc Pérez-Murano1, G. Rius2, J. Llobet1 and X. Borrisé3 1
Institut de Microelectrònica de Barcelona (IMB-CNM, CSIC). Campus de la UAB, 08193 Bellaterra. Spain. 2
Surface Science Laboratory. Toyota Technological Institute (TTI), 2-12-1 Hisakata, 468-8511 Nagoya. Japan 3
Institut Català de Nanotecnologia (ICN). Campus de la UAB, 08193 Bellaterra. Spain
ABSTRACT We present the development of CMOS compatible focused ion beam (FIB)-based method for the fabrication of nanomechanical devices. With only two step process, (i) patterning by direct exposure of silicon by the gallium beam and (ii) transfer of features to the structural layer by standard microfabrication silicon etching processes, operational devices are obtained. The ion beam modified silicon, acting as the etching mask, presents an outstanding robustness for both chemical and reactive ion etching process, enabling a simplified fabrication of nanomechanical devices with sub-micron resolution. As an example, single and double clamped silicon beams have been successfully produced. The compatibility check to guarantee the integrity of the electronic performance of CMOS circuits after the energetic beam irradiation is also investigated. Patterning based on direct ion beam exposure of silicon and etching presents advantages in comparison with more conventional lithography methods, such as electron beam lithography, since it is realized without the use of any resist media, which is especially challenging for the non-flat CMOS pre-fabricated substrates. INTRODUCTION Nanomechanical structures and nanoelectromechanical systems (NEMS) have a high potential to provide solutions for improving the performance of miniaturized systems in telecommunication, sensing or energy saving. A nanomechanical device is a structure whose function is based on exploiting its mechanical properties (elasticity, resonance frequency, quality factor) [1]. Example of functional nanomechanical structures are cantilevered and, double clamped beams or nanowires. In order to provide a determined function (actuation, transduction, etc), the operation of a nanomechanical structure can be static or dynamic. In static mode, the deflection of the structure as a function of external or internal forces is used as the relevant magnitude. In dynamic mode, the nanomechanical structure is actuated at one or several of its resonance frequencies. Nanomechanical structures operated in dynamic mode are used to build extremely sensitive mass sensors [2-6]. When a small quantity of mass is loaded on a nanomechanical structure, its resonance frequency changes. Monitoring the change of resonance frequency, the increase or
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decrease of mass can be monitored. The smaller the dimensions of the structure are, the more sensitive the device results. However, when the dimensions of the devices are reduced to submicron dimensions, experimental determination of the response of the device becomes challenging, being difficul
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