We have investigated interactions between plasma and organic polymer surfaces, using molecular dynamics (MD) simulations. Preliminary investigations are carried out based on the Brenner's interatomic potential model for hydrocarbon systems [1]. We have also developed a new interatomic potential model for hydrogen-nitrogen-carbon systems [2]. Various organic materials with low dielectric constants (low-k) have been investigated experimentally as insulating materials for future integrated circuits (IC) chips [3]. Such low-k materials typically contain chains of benzene rings. In this work, therefore, we consider poly (1,4-phenylene) [PPP] as a model substrate and examine its etching and deposition characteristics when it is exposed to hydrocarbon and N2/H2 plasmas. In actual processes, organic polymers are often etched by N2/H2 plasmas. However, from the point of view of numerical simulation, PPP etching/deposition processes by hydrocarbon plasmas are much simpler as this system contains only C and H as the constituent atoms. Before starting realistic simulations for actual polymer etching processes, we first look into plasma-surface interactions between PPP and hydrocarbon plasmas.
We note that carbon and nitrogen atoms share some similar characteristics. For example, they have similar masses and bond energies with other atoms. Given these facts, our MD simulations of hydrocarbon plasma etching may give some insight into more realistic N2/H2 plasma etching of organic polymers. In our MD simulations, we study interactions of a PPP surface with CHx (x=0-4) and Hy (y=1,2) beams, using a well-known potential model for the hydrocarbon system proposed by Brenner [1]. Based on the simulation results, we shall discuss polymer surface reaction mechanisms of polymer etching processes. We also expect differences in etching characteristics between C and N atoms [such as the numbers of their valence electrons] cannot be ignored. This difference is likely to manifest itself in MD simulations of polymer-NHx (x=0-3) beams using the new potential functions for the H-C-N system. In this presentation, we shall give details of this new potential model.

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