Study of high aspect ratio etching in silicon by a mixture of SF 6 /O 2 using a 2-D model based on a Monte Carlo approac
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A5.78.1
Study of high aspect ratio etching in silicon by a mixture of SF6/O2 using a 2-D model based on a Monte Carlo approach. G.Marcos1, A.Rhallabi1 and P.Ranson2 1.LPCM-IMN laboratory, UMR 6502, CNRS-University of Nantes, 2 rue de la Houssinière, B.P. 32 229, 44 322 NANTES Cedex 3, France. 2.GREMI-ESPEO, UMR 6606, CNRS-University of Orléans, 14 rue d'Issoudun, B.P. 6744, 45067 ORLEANS Cedex 2, France. E-Mail: [email protected]
ABSTRACT The subject of this paper is to describe and comment on results from an etching model based on Monte Carlo method. It calculates the temporal profile evolution of the silicon substrate under an SF6/O2 plasma chemistry and a cryogenic process. This work was conducted in correlation with an experimental set-up to ensure the validity of the final results. Some in-situ measurements obtained in the gas phase allowed estimation of the incident kinetic parameters such as main ion and neutral fluxes. Collisionless sheath model is connected to the surface model to determine energetic and angular ion distribution functions. The study focuses on final properties of deep and thin trenches used in new power components. The development of a simulation tool appears as an useful mean to understand the role of certain parameters not easily controlled by the etching machine. In this article, results concerning the topography and defects usually met during such an etching process are shown and discussed.
INTRODUCTION The emergence of new needs in microelectronics such as the realisation of microelectromechanical systems (MEMS) requires the development of rigorous, reliable and reproducible technological processes. In particular, the etching processes appear as critical steps for which the control of profiles and kinetic mechanisms are two fundamental subjects of research. Among the new applications, the integration of power components requires the installation of insulation zones between them in order to avoid the risks of electric discharge. On this topic, we study the transfer of deep trenches into the silicon wafer which are then filled by an insulating material as SiO2. In order to obtain these trenches, we set up a dry etch process which uses an SF6/O2 plasma chemistry in an ICP reactor. This process is cryogenic (a drop in the chuck temperature of around – 100°C), allowing a fluctuation in the chemical etching mechanisms by the growth of an oxide layer on the trench sidewalls [1]. The main objective of the experimental study is to define an industrial etching process which makes it possible to etch anisotropic trenches with high aspect ratio (AR > 50), under significant etching rates (ER > 5 µm/min) and with very weak topographic defects. But a study limited to machine parameters does not provide a complete understanding of the different chemical and physical mechanisms occurring during this type of process. For example, the role of mask geometry on the profiles properties is not easy to evaluate. Moreover, certain processes are coupled and it is not obvious to determine
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