Modeling of N₂/H₂ Plasma for Low-k Material Etching in a Capacitively Coupled Plasma Device

As the scale of semiconductors shrinks and the interconnect layer develops to ten's level, the resistance-capacitance (RC) delay of signals through interconnection materials becomes a big obstacle for high speed operation of integrated circuit. For the fast operation of device, RC (product of resistivity and capacitance) delay must be made smaller. The resistivity is determined by the interconnect material and capacitance, by dielectric material. In order to meet the requirement, low resistivity Cu metal and low dielectric constant (low-K) materials are used. Among the many candidates for the low-K inter-metal dielectric (IMD) materials, organic materials will be promising candidates. As a result, new etching conditions must be developed to match the material properties. In this research, we present the modeling results of a two-frequency capacitively coupled plasma (2f-CCP) with H₂/N ₂ gas mixture which includes neutral-species transport model, based on the relaxation continuum (RCT) model. Not only the plasma transport and spatial distribution, but also those of neutral gas are important issue for the etching process. Especially in H₂/N₂ plasma, NH _x neutrals have a big influence on the etching of organic materials. Moreover the distributions of excited species influence the plasma density and profile. Therefore we include the neutral transport model as well as plasma one in this calculation. The plasma and neutrals are calculated self-consistently by iterating the simulation of both species till a spatiotemporal steady state profile could be obtained. In the simulation of neutral species, the interactions of excited states, vibrational levels of both H₂ and N₂ molecules, and NH_x molecules are considered.