Invited Paper PS-WeM9
Beam Studies of Plasma Etching Reactions

Wednesday, October 30, 2013, 10:40 am, Room 104 C

For the development of highly integrated semiconductor devices, more precise control of etchingprocesses is required for further progress. For this purpose, it is desirable to have full understanding of surface reaction mechanisms associated with the etching processes. However, in general, it is difficult to analyze such reactions in detail for plasma etching processes because a large number of reactions take place simultaneously. One way to tackle this challenge is use a beam system to examine specific beam-surface interactions that are likely to take place in actual plasma etching processes. Pioneering work by Coburn et al.[1]using beam experiments clearly showed that silicon etching reactions on fluorinated surfaces are enhanced by energetic inert ion bombardment.Many such studies have provided useful qualitative information on silicon etching by plasmas based on, for example, halogen gases.As new advanced semiconductor devices have been proposed, thevariety of materials that require highly controlled etching and that of gases that are used for the reactive ion etching (RIE) processes have increased significantly. Therefore we believe that needs for such beam studies are higher than ever. Based on an earlier beam system [2], we have recently advanced our techniques to examine interactions of reactive ions and free radicals with material surfaces, using a multi-beam system. With this system, we have obtained detailed information onreactive etching and physical sputtering processes on various materials such as silicon, silicon oxide, silicon nitride, and metals including ferromagnetic materials. The multi-beam system is a mass-selected ion beam injector combined with supersonic molecular beam and effusive molecular beam sources. When a sample is irradiated with any combination of these beams, it exhibits a specific surfacereaction that would take place in an actualplasma.Its surface analyses include in-situ chemical analyses by X-ray photoelectron spectroscopyandFourier transform infraredspectroscopy and angular and time-resolved measurements of desorbing molecules bya rotatable QMS. In the presentation, a detailed account will be given of how such beam experiments unveil surface reaction mechanisms for RIE processes, based on examples ofour recent studieson selective etching processes of Si-based materials and metals.[1] J. W. Coburn, H. F. Winters, and T. J. Chuang: J. Appl. Phys 48(1997) 3532.[2]K. Karahashiet al.: J. Vac. Sci. Technol. A 22(2004) 1166